High-pressure liquid chromatographic-mass spectrometric determination of sorbic acid in urine: verification of formation of trans,trans-muconic acid.

An LC-MS method is described for the determination of urinary sorbic acid (SA), a common food additive, which allows to measure down to 4 microg/L of the compound. The method involves an acidic hydrolysis followed by solid-phase extraction. The method was applied to two volunteers who ingested SA and to 36 individuals with no dietary restriction. The results confirm that a little aliquot of ingested SA is found in urine also in humans. The significant correlation found between urinary levels of SA and trans,trans-muconic acid (MA) seems to indicate that the measurement of SA in urine could allow to estimate the amount of MA excreted following a dietary intake of SA and, consequently, to enhance the specificity of MA as a biomarker of benzene exposure. A point of clarification in future studies will be the actual chemical form of SA excreted, since our results clearly demonstrate that without hydrolysis only a very little amount of SA can be found even in subjects heavily exposed to SA.